Executed lines reported as missing in threads

Originally reported by k3it (Bitbucket: k3it, GitHub: k3it)

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I apologize for a cross post from http://stackoverflow.com/q/43991865/1653558 but it looks like this is a better place for the report

I’m getting some low coverage numbers on script with threads activated with a run() method. It seems that the coverage module is unable to keep track of all hits. Here is the code that demonstrates the problem. Running it should produce 100% coverage, but I’m getting 71.

#!python

from threading import Thread

class MyNestedThread(Thread):
        def run(self):
                print("hello from the nested thread!")

class MyThread(Thread):
        def run(self):
                print("Hello from thread")
                t = MyNestedThread()
                t.start()
                return

if __name__ == '__main__':
        for i in range(3):
                t = MyThread()
                t.start()

#!python


Hello from thread
hello from the nested thread!
Hello from thread
Hello from thread
hello from the nested thread!
hello from the nested thread!

Name     Stmts   Miss  Cover
----------------------------
foo.py      14      4    71%

re-running ‘coverage run foo.py’ sometimes gives a different %, and even 100% on occasion.

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• Bitbucket: https://bitbucket.org/ned/coveragepy/issue/582

[nedbat]

Threads won’t be measured unless you specify them as part of your concurrency setting:

concurrency = multiprocessing,thread

[JannisNe]

Hi, I found this thread when looking for a solution to a problem I wrote up here.

I am also having trouble measuring coverage in threads. I do join() my threads as suggested in this thread so that does not seem to be the problem. You can see the link above for additional info on the environment. I’d be grateful for any help!